This invention relates to photoflash lamps and particularly to photoflash lamps which are percussively ignited.
The invention also relates to methods of making lamps of the above variety.
Percussively-ignited photoflash lamps are well known in the art with examples being described in the following U.S. Patents, all of which are assigned to the assignee of the present invention:
1. U.S. Pat. No. 3,600,120 (B. Kopelman)
2. U.S. Pat. No. 3,700,377 (S. V. Brown)
3. U.S. Pat. No. 3,730,669 (J. W. Shaffer)
4. U.S. Pat. No. 3,771,941 (E. G. Audesse et al)
5. U.S. Pat. No. 3,918,883 (D. E. Armstrong et al)
As shown therein, such lamps typically include an envelope of light-transmitting material (e.g. glass) with a metallic primer tube sealed through a wall thereof. Deformation of the tube causes deflagration of the primer material therein up through the tube to ignite a combustible material (e.g. shredded zirconium) within the envelope. Other variations of percussively-ignited lamps are shown in U.S. Pat. Nos. 3,606,607 (J. W. Shaffer) and 3,706,521 (B. Kopelman et al), said patents also assigned to the assignee of this invention. The process for making these lamps involves sealing a metallic component having the desired primer mixture therein about a base or bottom portion of the glass envelope.
Yet another example of a percussively-ignited photoflash lamp is described in German Offenlegungsschrift No. 2161365. Ignition of this lamp is accomplished only by rupturing the destroyable envelope using a primer-type ignition means located outside the lamp's envelope.
A disadvantage inherent in lamps utilizing a metallic primer within the wall of a glass envelope or about the bottom portion thereof involves the proper sealing of these components. A mismatch in the seal region results in stressed or cracked seals which can render these lamps inoperable. Proper seals are possible, provided suitable materials are used in continuous care is taken during manufacture. Another disadvantage of these lamps is that relatively few glass compositions can be sealed economically to metal or metal alloy primer tubes. One of the best matches known to date involves mating Sylvania "No. 4 Alloy" with G-1 soda lead (soft) glass. Ideally, however, it is preferred to use the harder glasses which as Vycor (high silica) or quartz for lamp envelopes but these compositions do not render themselves to high speed manufacturing techniques involving glass-to-metal sealing.
Understandably, a disadvantage inherent in German Offenlegungsschrift No. 2161365 is the requirement for rupturing the lamp's envelope. Because most percussive lamps contain a pressurized combustion-supporting atmosphere therein, rupturing the envelope to provide ignition will present an extremely hazardous condition to the operator of the camera which utilizes the lamp.
It is believed, therefore, that a precussively-ignited photoflash lamp which eliminates the need for glass-to-metal or similar type within the lamp's envelope would constitute a significant advancement in the art. It is also believed that a new method for making such a lamp would constitute an advancement in the art.